Gantry presses have been used in the assembly of trusses used in a variety of applications. Typically, trusses are constructed on a work surface using a truss template. The work surface is typically composed of wooden or plastic panel materials. Typically a series of top and bottom connector plates are used to assemble chord and web members together in a truss assembly. A gantry press can be used to embed the connector plates into the truss members to assemble the truss.
The gantry press enables a manufacturer to decrease the time required to construct a truss. However, with repeated uses, the work surface compresses, increasing the distance between the work surface and the roller press, limiting the effectiveness of the roller press to embed the connector plates into the members. When the panels forming the work surface are changed, replaced or compressed by the roller press, the distance between work surface distance changes.
At times wooden members used in the truss assembly are harder or denser than usual. Embedding the connector plates in the denser materials requires that the vertical adjustment of the gantry press with respect to the work surface would have to be altered along the length of the roller press to account for the variation in density between soft materials and denser materials. In the case of harder woods or denser materials, the roller press must be changed to account for the increased amount of pressure caused by the resistance of the connector plates to embed in the truss members.
The conventional method to adjust the parallel roller requires a workman to manually adjust each side of the gantry press and check for proper spacing and parallel orientation with the work surface to acquire the proper vertical adjustment. In prior gantry presses, a nut and bolt rod assembly is connected to the roller press to allow for vertical adjustment where each side of the roller press would be manually and individually adjusted. An example of such adjustment apparatus is shown in U.S. Pat. No. 3,855,917 issued to Farrell et al. If the roller press spacing needs to be lowered, gauge blocks are placed between the work surface and the roller press. The roller press would then be lowered on each side until the roller press encountered the gauge blocks. If the roller press is to be raised, then a different gauge block designating the desired depth is placed between the work surface and the roller press. Again, the workman would manually lower each side of the roller press to the proper depth, and the press is verified to be in a parallel orientation with the work surface for proper operation of the gantry press.
Present gantry presses enable the roller press to disengage the truss assembly by vertically raising the roller press. For example, U.S. Pat. No. 5,211,108 issued to Gore et al. discloses an apparatus for selectively raising and lowering the roller press in a gantry press. To reduce the cycle time between successive operations, the roller press is automatically raised when the gantry press has stooped so that the completed truss can be discharged, eliminating the need for a side discharge table and to eliminate the need to initiate a manual lifting operation of the roller press to remove the truss.
Thus, a need exists for a gantry press with a vertically adjustable roller press which can be readily lowered or raised a discrete amount in a parallel fashion with a work surface and then used to complete assembly of the truss. Such a device would reduce labor costs and decrease the amount of setup time needed to place the gantry press into a proper configuration.